What is the recommended oral iron supplementation regimen for patients with iron deficiency anemia?

Oral Iron Supplementation for Iron Deficiency Anemia

The recommended oral iron supplementation regimen for iron deficiency anemia is ferrous sulfate 200 mg (65 mg elemental iron) once daily, taken on an empty stomach, and continued for approximately 3 months after hemoglobin normalization to ensure adequate repletion of iron stores. 1, 2

First-Line Iron Formulation

• Ferrous sulfate is the preferred first-line oral iron formulation as it is cost-effective with no proven advantages of other formulations in terms of efficacy 1, 2
• Standard ferrous sulfate tablets (200 mg) provide 65 mg of elemental iron per tablet 1, 3
• Alternative ferrous salts can be considered if ferrous sulfate is not tolerated:
  • Ferrous fumarate (provides 69 mg elemental iron per tablet) 1, 4
  • Ferrous gluconate (provides 37-38 mg elemental iron per tablet) 1, 5

Optimal Dosing Strategy

• Once-daily dosing of 50-100 mg elemental iron is recommended rather than multiple daily doses 1
• Taking iron on an empty stomach maximizes absorption, though this may increase gastrointestinal side effects 2, 6
• Alternate-day dosing may be considered for patients experiencing significant gastrointestinal side effects, as it may provide similar iron absorption with fewer adverse effects 1, 7
• Monitor hemoglobin response within 4 weeks of starting treatment 1, 6
• The absence of a hemoglobin rise of at least 10 g/L after 2 weeks of daily oral iron therapy strongly predicts subsequent treatment failure (sensitivity 90.1%, specificity 79.3%) 1

Strategies to Improve Absorption and Tolerability

• Take iron with vitamin C (250-500mg) to enhance absorption by forming a chelate with iron 1, 2, 7
• Avoid taking iron with tea, coffee, calcium, or antacids, which inhibit absorption 2, 6
• If standard doses are not tolerated, consider:
  • Reduced dose (one tablet every other day) 1
  • Taking with food (though this reduces absorption by 40-66%) 2, 6
  • Switching to an alternative iron formulation 1, 2

Duration of Treatment

• Treatment should be continued for approximately 3 months after hemoglobin normalizes to ensure adequate repletion of marrow iron stores 1, 2, 8
• After restoration of hemoglobin and iron stores, monitor blood counts periodically (perhaps every 6 months initially) to detect recurrent iron deficiency anemia 1, 6

When to Consider Parenteral Iron

• Intravenous iron should be considered when: 1, 6
  • Oral iron is contraindicated, ineffective, or not tolerated despite modifications
  • Patient has conditions where oral iron absorption is impaired (e.g., inflammatory bowel disease, post-bariatric surgery)
  • Ferritin levels do not improve with a trial of oral iron
  • Rapid correction of iron deficiency is needed

Common Pitfalls and Caveats

• Avoid modified-release preparations as they are generally considered "less suitable for prescribing" due to reduced iron absorption in the duodenum 2
• Do not use multivitamin preparations as the sole source of iron supplementation as they typically contain insufficient elemental iron for treating iron deficiency anemia 2, 6
• Restricted packed cell transfusion should be reserved only for those with severe symptomatic anemia and/or circulatory compromise, as it will not replenish the iron store deficit in severe IDA 1
• Switching between different traditional iron salts when experiencing side effects is not supported by evidence; consider alternate-day dosing, ferric maltol, or parenteral iron instead 1